<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>17-盒子-边线-内边距-外边距</title>
		<style type="text/css">
			/*
				需求：在500*500的盒子中放置一个200*200的电脑
			*/
		   .box{
		      width:500px;
		      height: 500px;
		      border:1px solid red;
		      margin:30px auto;
		   }
		   .box img{
		      width:200px;
			  height:200px;
			  display: block;
			  margin:150px auto;
		   }
		</style>
	</head>
	<body>
		
		<div class="box">
			<img src="images/20.png" alt="">
		</div>

	</body>
</html>
